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1991 camro No power to fuel pump
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thirdgennewie
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Jan 19, 2010, 1:35 PM
Post #1 of 15
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1991 camro No power to fuel pump
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ok so i was driving and the car just died out of the blue so i go to start and it wont turn over i tested the relays and the fuel pump fuse and their ok i think but i still dont hear the pump PRIME , unless i jump the pump from the relay, that is the only time i hear it. I cant find the oil pressure sending unit ??? can someone tell me where that is????/ any help would be greatly appreciated....thanks
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 19, 2010, 4:30 PM
Post #2 of 15
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Re: 1991 camro No power to fuel pump
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If jumping at the relay worked than I suspect it's no good. If the same as the A/C relay, swap them for a test to save $20 bucks at being wrong,
T
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thirdgennewie
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Jan 19, 2010, 4:51 PM
Post #3 of 15
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Re: 1991 camro No power to fuel pump
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what is no good???and i swapped them and both the relays work....thats why im looking for the opsu now..thanks
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 19, 2010, 5:05 PM
Post #4 of 15
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Re: 1991 camro No power to fuel pump
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You have three posts going on same car in one day! I answered that at another. Please don't multiple post like that it's confusing YOU and us,
T
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thirdgennewie
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Jan 19, 2010, 5:27 PM
Post #5 of 15
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Re: 1991 camro No power to fuel pump
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good sir i have 2 posts and am sorry for the excess but i neeed help man
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 20, 2010, 3:33 AM
Post #6 of 15
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Re: 1991 camro No power to fuel pump
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Don't be sorry - just realize it's counter productive to help you. I don't have every answer for every problem. Re the oil pressure switch/sender - there is a relationship in many GMs I believe but a grace period for start up as of course there's no oil pressure until it's running.
Guess for you until someone else may have a better idea is that the trigger wire for that relay from ign switch is not making it to relay. For now, and I don't know (retired and won't pay for the software) you need to know which wire empowers the relay and trace back to find the break in power. It could even be at a rubber like block at the firewall - not sure,
T
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steve01832
Veteran
Jan 20, 2010, 5:00 PM
Post #7 of 15
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Re: 1991 camro No power to fuel pump
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The oil pressure sending unit is only a backup if the relay fails. You will have an extended crank time until the oil pressure builds up, then the sender closes supplying voltage to the pump. The relay is constant. I will try to find the wiring diagram for you.
Steve
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asleepatdawheel
User
Jan 20, 2010, 11:55 PM
Post #8 of 15
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Re: 1991 camro No power to fuel pump
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Im not for certain but the switch does run with the f/p relay and gives power if relay open when engine is running..If relay is no good then pump gets power from o/p switch after cranking... So if you have power to pump while cranking and no start ... I would suspect pump... If no power going to pump after cranking for a few seconds I would check relay then switch.. Also I believe there should be a test connection in your wire loom by the master cylinder so you can power up the pump to check fuel pressure... Dont qoute me on all of this but have some knowledge of chevy cars and trucks as to what to look for...
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Its not called bragging,, if you can back it up....
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thirdgennewie
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Jan 21, 2010, 7:55 AM
Post #10 of 15
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Re: 1991 camro No power to fuel pump
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the engine cranks but will not start and run , the only time i hear the pump prime is when i jump the pump at the relays, i have a RS also with a 5.0 l engine
thanks
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Sidom
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/ Moderator
Jan 21, 2010, 11:27 AM
Post #11 of 15
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Re: 1991 camro No power to fuel pump
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I think on this one you should back up just a bit. 1st I think I would verify that this is a fuel suplpy problem. Get a can of carb clean and spray down the throttle body and see if the engine will run on that. If it is a fuel supply problem the engine should start for a few seconds or as long as you spray the carb clean. You said it's a 5.0 so this should be a TBI system - low pressure.
You can't go by listening to the pump to tell if it's good or bad, you really need to hook up a fuel pressure gauge to verify pressure. To check power you will need a helper, the system only powers up for 2 seconds with the koeo. To check for power you need to go back to the pump & check the gray wire for power with the key on.
But 1st things 1st, the easiest thing to do would be to spray some starting fluid or carb clean down the throttle body to see it the engine starts, if it won't run on that it could be something as simple as a control module gone bad not giving you an injector pulse.
Have you check for spark yet?
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thirdgennewie
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Jan 28, 2010, 8:22 PM
Post #12 of 15
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Re: 1991 camro No power to fuel pump
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Ok here's where we are at. No fuel pump signal to the relay while starting. 10.8v between the orange and gray wires on the FP relay connector when ignition switch is in the on or off position but no start. If I jump gray wire at connector with known good 12v supply the FP runs and car starts. When I measure volts between Orange and gray wire with the car running I get 12v. Disconnected the OPSU, 3 wire, red,yellow,black, and tried to start. Nothing. Jumped and measured voltage at red and black wires at OPSU (2.4v) and nothing. Relay is good. FP fuse is good. Where should I look next? Seems like I am not getting a signal to prime the FP.
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Sidom
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Jan 29, 2010, 8:45 PM
Post #13 of 15
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Re: 1991 camro No power to fuel pump
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Looks like the orange wire going to the oil press sending unit should have 12v on it, this could be part of your problem.
This diagram should help you track things down.
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wrenchjock
New User
Jun 8, 2010, 7:06 PM
Post #14 of 15
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Re: 1991 camro No power to fuel pump
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there may be a fuse on the inside of the right hand fender , beside the battery , replace if blown and you;ll be just fine
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Hammer Time
Ultimate Carjunky
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Jun 8, 2010, 7:14 PM
Post #15 of 15
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Re: 1991 camro No power to fuel pump
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this thread is 6 months old. There is no point in responding to something this old.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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